The present invention relates to a fluid-quenched circuit breaker.
It is to be noted that FR-A-2 519 470 discloses a fluid quenched
circuit breaker in which there are shown a movable arc contact of the "tulip" type,
a bell-shaped element of electrically insulating material and two chambers for
the passage of the arc quenching fluid.
US-A-4 289 942 and FR-A-2 518 978 substantially disclose circuit breakers similar
to the above mentioned one.
The energy developed by the electrical arc, while heating the gas,
decomposes it, generating a pressure which provides a blast of fluid onto the arc,
causing it to be quenched.
According to known solutions, interruption chambers are equipped
with elements of electrical insulating material, provided with suitably shaped
and orientated openings, which allow the gas to circulate under pressure, to accomplish
Such types of chambers, due to the difficulty of accomplishing the
optimum conditions required for the interruption of the currents throughout the
range provided by the operations, i.e., from the small overload up to the highest
interruption powers, are characterized by a narrow operation range, i.e., if the
dimensioning is designed to interrupt high currents, do not result effective in
quenching the lower currents, and vice-versa.
Purpose of the present invention is to obviate the disadvantages
of the cited prior art, by providing a universal interruption chamber, which, on
the basis of its inner geometry, allows the necessary gas pressures and speeds,
and hence high interruption powers to be generated without losing efficaciousness
when the interruption of the lowest overload currents is required.
In order to achieve such a purpose, the present invention provides
a fluid-quenched circuit breaker having the features claimed in claim 1.
The characteristics and the advantages of the present invention shall
appear more clearly from the following disclosure, referred to the attached drawings,
- Fig. 1 is a partially sectional exploded view of a first embodiment of a fluid
quenched circuit breaker according to the invention,
- Fig. 2 is a plan view of the intermediate element of Fig. 1,
- Fig. 3 is a sectional elevation view of the elements of Fig. 1, in their assembled
- Fig. 4 is a sectional view along the path IV-IV of Fig. 3,
- Fig. 5 is a sectional elevation view of a second embodiment of the interruption
chamber according to the invention, and
- Fig. 6 is a sectional elevation view of a second form of practical embodiment
of the interruption chamber according to the present invention.
Inside a tightly sealed electrical insulating encasing (not shown
in the Figures; also other structural parts not strictly relating to the invention
have not been shown) containing an arc-quenching gas such as sulphur hexafluoride,
there are provided current-bearing connections, respectively bearing a movable
main contact 20 and a stationary main contact 20bis, together with the related
arc contact 11 (the movable contact) and 11bis (the stationary contact).
Referring to the figures, there is shown a movable arc contact 11
of tubular type with longitudinal notches, or more precisely of the tulip type,
positioned inside a bell-shaped element 12 of electrical insulating material,
solid with the said movable contact, which surrounds it, and is positioned above
the said arc contact 11.
The movable arc contact 11 and the inner surface 37 of the element
12 define a first chamber 13 comprised therebetween.
The movable arc contact 11 has an upper portion made of petals 14
radially enlarged upwards, and at the connection of which there are provided radial
discharge holes 15.
An intermediate portion 16 radially enlarged to a ring-shape separates
a lower threaded portion 17, suitable to be screwed within a complementary seat
18 centrally provided in a body 19 of a movable main contact 20.
Also from the bell-shaped element 12 a cylindrical threaded portion
21 protrudes downwards and it can be positioned within a complementary threaded
seat 22, provided in the body 19 of the main movable contact 20 and externally
concentric to the seat 18.
On its outer surface, the bell-shaped element 12 is provided with
protruding portions 23, e.g., with four of them, running along generatrices thereof,
bent towards a nozzle 24.
Coaxially arranged around said first chamber 13, a second chamber
25 is defined in its upper portion on one side by the element 12 and on the other
side by a wall of electrical insulating material 26 having a crown 27, in which
there is provided a nozzle-shaped opening 28.
The lower portion of chamber 25 is defined by the inner walls 29
of the body 19 on one side and on the other side by a corresponding lower outer
portion of the element 12 A set of four holes 30 is positioned on an annular portion
31 of the body 19, concentric to said threaded seats 18 and 22.
The wall of electrical insulating material 26 and the movable main
contact 20 are connected to each other by respective annular, threaded and complementary
undercuts 32 and 33 coupled with each other, creating one single outer body.
During the opening of the main contacts 20 and 20bis, the electrical
arc is generated between the arc contacts 11 and 11bis,. By overheating the surrounding
arc-quenching medium, the arc causes it to flow, under pressure, inside the coaxial
chambers 13 and 25 and inside the movable arc contact 11.
In particular, inside the chamber 25 the gas flows upwards, passing
into a zone 34 at lower speed and pressure, and into a zone 35, of smaller volume,
at higher speed and pressure. In this way, in the area wherein the electrical
arc is generated, a more uniform and effective gas blast action is obtained, which
allows a reduction in the arc-quenching times and hence a lower and more uniform
wear of the top portion of element 12.
Furthermore, the particular profile of the bell-shaped element 12,
and in particular the protruding portions 23 allow the gas pressure to be varied
in the compression step during the opening of the contacts. As a consequence there
is a reduction in the volume of the pumped gas and an increase in capacity of interruption,
with the diameters of the stationary arc contact and of the movable arc contact,
and the diameters of components 24-27 and 28 being the same.
As to the chamber 13, the suitably shaped discharge holes 15 allow
the generation of a depression in an upper zone 36 of the movable arc contact 11
wherein the arc is generated. Such a depression allows the removal of heat from
the zone 36 wherein the arc is generated, increasing the interruption power in
that the arc which is generated on contacts opening is cooled more rapidly.
In another embodiment of the interruption chamber of the invention
and shown in Fig. 5, element 12 is internally and in its lowermost portion provided,
with a recessed portion 38, which defines, together with the movable contact 11,
a volume greater than that defined by the homologous straight portion 37 of Fig.
A further embodiment of the interruption chamber, according to the
present invention, is shown in Fig. 6, with a movable contact 111 shaped as to
have in its interior a portion 140 made of electrical insulating material, which
modifies the gas discharge from the zone 113 towards the direction 141. In a similar
way as in Fig. 3, the movable arc contact 111 is housed inside a seat 118 centrally
provided in a body 119 of a movable main contact 120.
Coaxially with and externally to the seat 118 a suitably dimensioned
annular through-hole 121 is provided, which places the chamber 113 in communication
towards the bottom 142 with the remaining of the electrical insulating encasing
In such a way, the chamber 113 and chamber 142 act, for certain current
values, as a function of the diameter of hole 121 and of the volumes of chambers
113 and 142, as a double chamber for receiving the overheated gas, which flows
downwards under its self-generated pressure. When the gas flows through the annular
hole 121, quenching of the arc by heat removal from the arc zone during the passage
of the arc current is achieved, and subsequently the current is in the proximity